A case that needs a control to turn on/off an output in a short-term period for purposes of enhancing efficiency of a system or others becomes a background thereof.
Particularly, for purposes of increasing a rotation speed of a motor, for example, in the motor, a motor inductance for obtaining a sufficient voltage margin in a high-speed operating region is reduced and a three-phase ripple current is increased due to the reduction of the motor inductance, and therefore efficiencies of the motor and an inverter supplying a driving current thereto are reduced.
Particularly, in case of operating a motor at a low speed in response to demand for a small output, a three-phrase current is small and a ripple current increases, and therefore the effect of reduction of efficiency remarkably appears. Further, there was a problem that a switching loss of an IGBT in the inverter occurred and therefore efficiency thereof reduced.
For solving the problems, there developed a technology that repeatedly, in a short-term period, turns on/off a driving current applied to the motor from the inverter in the period that the motor operates at a low speed and therefore saves power consumption thereof. A period of the On/Off and a duty of the On/Off may be set as a value that may secure stability of operation with a minimum of power consumption, and therefore there have the effects that enhance efficiency and stability of operation.
However, in the case that an integration process is included for the feedback control in the feedback-controlling of the driving current in the controller controlling the inverter, there occurred the problems that a value of the driving current measured in the period that the driving current was turned off became o and therefore an error between the measured value and a target value was rapidly increased. A control value was greatly outputted due to the excessively increased error integral value and again due to the foregoing, the driving current outputted from the inverter was severely oscillated.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.